Currently, a belt commonly used as a reinforcing member for a carcass being a bone structure in a radial tire for a passenger car, particularly a reinforcing member for a crown portion of the carcass is mainly constituted by using two or more belt layers each composed of a rubberized layer containing steel cords arranged slantly with respect to an equatorial plane of the tire and crossing the steel cords of these belt layers with each other.
Also, a belt reinforcing layer formed by rubberizing reinforcing elements such as nylon cords or the like may be disposed on an outside of the belt in a radial direction of the tire in order to improve the stability during the running of the tire, particularly the stability during the high-speed running and further improve the durability of the tire by preventing the peeling of the belt layer during the high-speed running, particularly the peeling notably caused at end portions of the belt layer. As the structure of the belt reinforcing layer is known a so-called cap-layer structure or the like. The stability during the running of the tire can be improved by disposing the belt reinforcing layer containing the reinforcing elements such as nylon cords or the like to suppress a size growth of the tire in the radial direction during the running.